vb.net 标签文本不一一更新 Visual Basic
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Label text not updating one by one Visual Basic
提问by DemCodeLines
I have this custom class
我有这个自定义类
Public Class labelScroll
Inherits Label
Public Shadows Property Text As String
Get
Return MyBase.Text
End Get
Set(ByVal value As String)
Dim add As String = ""
Dim result As String()
Dim i As Integer
result = Split(value, vbLf)
Dim n As Integer = 30
If (result.Length < n) Then
n = result.Length
End If
Dim start As Integer = result.Length - n
For i = start To result.Length - 1 Step 1
add += result(i) + Environment.NewLine
Next
MyBase.Text = add
End Set
End Property
End Class
I have a form that I placed this labelScroll on and also placed a button: I have this code for the button's click event:
我有一个表单，我在上面放置了这个 labelScroll 并放置了一个按钮：我有这个按钮点击事件的代码：
Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
LabelScroll1.Text = "1"
Threading.Thread.Sleep(1000)
LabelScroll1.Text += "2"
Threading.Thread.Sleep(1000)
LabelScroll1.Text += "3"
End Sub
What happens when I click the button is that it takes 2 seconds and then just shows "1" "2" "3" on three lines. What actually should happen is that when the user clicks the button, "1" appears and then Threading.Thread.Sleep(1000)is executed so the program waits for 1 second then prints "2" on the next line.
当我单击按钮时会发生什么，它需要 2 秒钟，然后只在三行上显示“1”“2”“3”。实际应该发生的是，当用户单击按钮时，会出现“1”然后Threading.Thread.Sleep(1000)执行，因此程序等待 1 秒，然后在下一行打印“2”。
Why isn't this happening?
为什么这不发生？
回答by Will A
Setting the text on a label invalidates the control - meaning it will redraw the next time the event queue is processed (effectively). This won't happen whilst you're sleeping on the UI thread - try adding MyBase.Update()immediately after the MyBase.Text = ... line to force an immediate update.
在标签上设置文本会使控件无效 - 这意味着它将在下次处理事件队列时（有效）重绘。当您在 UI 线程上睡觉时，这不会发生 - 尝试MyBase.Update()在 MyBase.Text = ... 行后立即添加以强制立即更新。
